Accessing imgUr thru OAuth (uploading to user account)

Question

To start doing this \"simple\" task I\'ve researched for a procedure that I\'ve taken as an example here to follow and reproduce the steps, the procedure can upload an image

Answer 1

This is long, because it is more or less a compleat API:

Public Class imgurAPI
    ' combination of this API and imgUR server responses
    Public Enum imgUrResults
        OK = 200                        ' AKA Status200 

        ' errors WE return
        OtherAPIError = -1              ' so far, just missing ImgLink
        InvalidToken = -2
        InvalidPIN = -3                 ' pins expire
        InvalidRequest = -4
        TokenParseError = -5

        ' results we get from server
        BadRequestFormat = 400          ' Status400   
        AuthorizationError = 401        ' Status401  

        Forbidden = 403                 ' Status403   
        NotFound = 404                  ' Status404   ' bad URL Endpoint
        RateLimitError = 429            ' Status429   ' RateLimit Error
        ServerError = 500               ' Status500   ' internal server error

        UknownStatus = 700              ' We havent accounted for it (yet), 
                                        '   may be trivial or new
    End Enum

    ' container for the cool stuff they send us
    Friend Class Token
        Public Property AcctUserName As String
        Public Property AccessToken As String
        Public Property RefreshToken As String
        Public Property Expiry As DateTime

        Public Sub New()
            AcctUserName = ""
            AccessToken = ""
            RefreshToken = ""
            Expiry = DateTime.MinValue
        End Sub

        Friend Function IsExpired() As Boolean

            If (Expiry > DateTime.Now) Then
                Return False
            Else
                ' if expired reset everything so some moron doesnt
                ' expose AccessToken and test for ""
                AcctUserName = ""
                AccessToken = ""
                RefreshToken = ""
                Expiry = DateTime.MinValue
                Return True
            End If
        End Function

    End Class

    ' NO simple ctor!!!
    ' constructor initialized with ClientID and SecretID
    Public Sub New(clID As String, secret As String)
        clientID = clID
        clientSecret = secret
        myPin = ""
        imgToken = New Token
        LastImageLink = ""
        UseClipboard = True
        AnonOnly = False
    End Sub

    ' constructor initialized with ClientID and SecretID
    Public Sub New(clID As String)
        clientID = clID
        clientSecret = ""
        myPin = ""
        imgToken = New Token
        LastImageLink = ""
        UseClipboard = True
        AnonOnly = True
    End Sub


    Private clientID As String
    Private clientSecret As String

    Private AnonOnly As Boolean = True

    ' tokens are not public
    Private imgToken As Token

    Public Property LastImageLink As String

    Public Property UseClipboard As Boolean

    ' precise moment when it expires for use in code
    Public ReadOnly Property TokenExpiry As DateTime
        Get
            If imgToken IsNot Nothing Then
                Return imgToken.Expiry
            Else
                Return Nothing
            End If
        End Get
    End Property

    Public Function GetExpiryCountdown() As String
        Return String.Format("{0:hh\:mm\:ss}", GetExpiryTimeRemaining)
    End Function

    ' time left as a TimeSpan
    Public Function GetExpiryTimeRemaining() As TimeSpan
        Dim ts As New TimeSpan(0)

        If imgToken Is Nothing Then
            Return ts
        End If

        If DateTime.Now > imgToken.Expiry Then
            Return ts
        Else
            ts = imgToken.Expiry - DateTime.Now
            Return ts
        End If

    End Function

    Public Function IsTokenValid() As Boolean

        If imgToken Is Nothing Then
            Return False
        End If

        If String.IsNullOrEmpty(imgToken.AcctUserName) Then
            Return False
        End If

        If imgToken.IsExpired Then
            Return False
        End If

        Return True

    End Function

    ' Currently, the PIN is set from a calling App.  Might be possible
    ' to feed the log in to imgUr to get a PIN
    Private myPin As String
    Public WriteOnly Property Pin As String
        Set(value As String)
            myPin = value
        End Set
    End Property


    ' Navigates to the web page.
    ' see wb_DocumentCompleted for code to 
    ' parse the PIN from the document
    Public Sub RequestPinBrowser(BrowserCtl As WebBrowser)

        If AnonOnly Then
            ' you do not need a PIN for Anon
            Throw New ApplicationException("A PIN is not needed for ANON Uploads")
            Exit Sub
        End If

        If BrowserCtl Is Nothing Then
            Throw New ArgumentException("Missing a valid WebBrowser reference")
            Exit Sub
        End If

        ' imgur API format
        ' https://api.imgur.com/oauth2/authorize?client_id=YOUR_CLIENT_ID&response_type=REQUESTED_RESPONSE_TYPE&state=APPLICATION_STATE

        Dim OAuthUrlTemplate = "https://api.imgur.com/oauth2/authorize?client_id={0}&response_type={1}&state={2}"
        Dim ReqURL As String = String.Format(OAuthUrlTemplate, clientID, "pin", "ziggy")

        BrowserCtl.Url = New Uri(ReqURL)
    End Sub


    Public Function GetAccessToken() As imgUrResults
        ' there are different types of token requests
        ' which vary only by the data submitted

        Dim sReq As String = String.Format("client_id={0}&client_secret={1}&grant_type=pin&pin={2}",
                                            clientID, clientSecret, myPin)
        If myPin = String.Empty Then
            Return imgUrResults.InvalidPIN
        End If

        If AnonOnly Then Return imgUrResults.InvalidRequest

        ' call generic token processor
        Return RequestToken(sReq)

    End Function

    ' request a Token 
    Private Function RequestToken(sRequest As String) As imgUrResults
        Dim url As String = "https://api.imgur.com/oauth2/token/"

        Dim myResult As imgUrResults = imgUrResults.OK

        ' create request for the URL, using POST method
        Dim request As WebRequest = WebRequest.Create(url)
        request.Method = "POST"

        ' convert the request, set content format, length
        Dim data As Byte() = System.Text.Encoding.UTF8.GetBytes(sRequest)
        request.ContentType = "application/x-www-form-urlencoded"
        request.ContentLength = data.Length

        ' write the date to request stream
        Dim dstream As Stream = request.GetRequestStream
        dstream.Write(data, 0, data.Length)
        dstream.Close()

        ' json used on the response and potential WebException
        Dim json As New JavaScriptSerializer()

        ' prepare for a response
        Dim response As WebResponse = Nothing
        Dim SvrResponses As Dictionary(Of String, Object)

        Try
            response = request.GetResponse
            ' convert status code to programmatic result
            myResult = GetResultFromStatus(CType(response, HttpWebResponse).StatusCode)

        Catch ex As WebException
            ' a bad/used pin will throw an exception
            Dim resp As String = New StreamReader(ex.Response.GetResponseStream()).ReadToEnd()

            SvrResponses = CType(json.DeserializeObject(resp.ToString), 
                                    Dictionary(Of String, Object))
            myResult = GetResultFromStatus(Convert.ToString(SvrResponses("status")))

        End Try

        'Console.WriteLine(CType(response, HttpWebResponse).StatusDescription)
        'Console.WriteLine(CType(response, HttpWebResponse).StatusCode)

        ' premature evacuation
        If myResult <> imgUrResults.OK Then
            If dstream IsNot Nothing Then
                dstream.Close()
                dstream.Dispose()
            End If
            If response IsNot Nothing Then
                response.Close()
            End If

            Return myResult
        End If

        ' read the response stream
        dstream = response.GetResponseStream
        Dim SvrResponseStr As String
        Using sr As StreamReader = New StreamReader(dstream)
            ' stream to string
            SvrResponseStr = sr.ReadToEnd
            'Console.WriteLine(SvrResponse)
        End Using

        ' close streams
        dstream.Close()
        dstream.Dispose()
        response.Close()

        Try
            ' use json serialier to parse the result(s)
            ' convert SvrRsponse to Dictionary
            SvrResponses = CType(json.DeserializeObject(SvrResponseStr), 
                                    Dictionary(Of String, Object))

            ' get stuff from Dictionary
            imgToken.AccessToken = Convert.ToString(SvrResponses("access_token"))
            imgToken.RefreshToken = Convert.ToString(SvrResponses("refresh_token"))
            imgToken.AcctUserName = Convert.ToString(SvrResponses("account_username"))

            ' convert expires_in to a point in time
            Dim nExp As Integer = Convert.ToInt32(Convert.ToString(SvrResponses("expires_in")))
            imgToken.Expiry = Date.Now.Add(New TimeSpan(0, 0, nExp))

            ' Pins are single use
            ' throw it away since it is no longer valid 
            myPin = ""

        Catch ex As Exception
            'MessageBox.Show(ex.Message)
            myResult = imgUrResults.TokenParseError
        End Try

        Return myResult


    End Function

    ' public interface to check params before trying to upload
    Public Function UploadImage(filename As String, Optional Anon As Boolean = False) As imgUrResults

        If AnonOnly Then
            Return DoImageUpLoad(filename, AnonOnly)
        Else
            If IsTokenValid() = False Then
                Return imgUrResults.InvalidToken
            End If
        End If

        ' should be the job of the calling app to test for FileExist
        Return DoImageUpLoad(filename, Anon)

    End Function

    ' actual file uploader
    Private Function DoImageUpLoad(fileName As String, Optional Anon As Boolean = False) As imgUrResults
        Dim result As imgUrResults = imgUrResults.OK
        LastImageLink = ""

        Try
            ' create a WebClient 
            Using wc = New Net.WebClient()
                ' read image
                Dim values = New NameValueCollection() From
                        {
                            {"image", Convert.ToBase64String(File.ReadAllBytes(fileName))}
                        }
                ' type of headers depends on whether this is an ANON or ACCOUNT upload
                If Anon Then
                    wc.Headers.Add("Authorization", "Client-ID " + clientID)
                Else
                    wc.Headers.Add("Authorization", "Bearer " & imgToken.AccessToken)
                End If

                ' upload, get response
                Dim response = wc.UploadValues("https://api.imgur.com/3/upload.xml", values)

                ' read response converting byte array to stream
                Using sr As New StreamReader(New MemoryStream(response))
                    Dim uplStatus As String
                    Dim SvrResponse As String = sr.ReadToEnd

                    Dim xdoc As XDocument = XDocument.Parse(SvrResponse)
                    ' get the status of the request
                    uplStatus = xdoc.Root.Attribute("status").Value
                    result = GetResultFromStatus(uplStatus)

                    If result = imgUrResults.OK Then
                        LastImageLink = xdoc.Descendants("link").Value

                        ' only overwrite the server result status
                        If String.IsNullOrEmpty(LastImageLink) Then
                            ' avoid NRE elsewhere
                            LastImageLink = ""
                            ' we did something wrong parsing the result
                            ' but this one is kind of minor
                            result = imgUrResults.OtherAPIError
                        End If
                    End If

                End Using

                If UseClipboard AndAlso (result = imgUrResults.OK) Then
                    Clipboard.SetText(LastImageLink)
                End If

            End Using
        Catch ex As Exception
            Dim errMsg As String = ex.Message

            ' rate limit
            If ex.Message.Contains("429") Then
                result = imgUrResults.RateLimitError

                ' internal error
            ElseIf ex.Message.Contains("500") Then
                result = imgUrResults.ServerError

            End If
        End Try

        Return result
    End Function

    Private Function GetResultFromStatus(status As String) As imgUrResults

        Select Case status.Trim
            Case "200"
                Return imgUrResults.OK
            Case "400"
                Return imgUrResults.BadRequestFormat
            Case "401"
                Return imgUrResults.AuthorizationError
            Case "403"
                Return imgUrResults.Forbidden
            Case "404"
                Return imgUrResults.NotFound
            Case "429"
                Return imgUrResults.RateLimitError
            Case "500"
                Return imgUrResults.ServerError
            Case Else
                ' Stop - work out other returns
                Return imgUrResults.UknownStatus
        End Select
    End Function

    Private Function GetResultFromStatus(status As Int32) As imgUrResults
        ' some places we get a string, others an integer
        Return GetResultFromStatus(status.ToString)
    End Function

End Class

HOW TO USE IT

The process requires a web browser for the user to navigate and request a PIN. For testing/development, I used a WebBrowser control and snagged the PIN from the returned page.

Note: for testing, my imgUR account was setup as DESKTOP, since we are sending from a DESKTOP app. Also, this is for YOU sending images to YOUR account. There is not a way for OTHERS to upload to YOUR account without giving out your secret ID and/or embedding your master ImgUR Login and password in the App. That is how ImgUR designed it.

A. Create an imgUR object:

Friend imgUR As imgurAPI
imgUR = New imgurAPI(<your Client ID>,<your secret code>)

B. Get a Pin - Method One

' pass the app's WebBrowser Control
imgUR.RequestPinBrowser(wb)

This will take you to a imgur page where you must authorize the issue of a PIN for uploading to your account. Enter your Account Name, Password, Click ALLOW. A new page with the PIN will be displayed. Copy the PIN from the webpage to some other control which can feed it to the imgurAPI Class.

There is code below to parse the PIN page and get it into another control.

Method Two

• Using your own external browser, go to

https://api.imgur.com/oauth2/authorize? client_id=YOUR_CLIENT_ID&response_type=pin&state=ziggy

• Log In
• Copy the PIN you receive into a TextBox or something to send it to the imgurAPI:
• Set pin: imgUR.Pin = <<PIN YOU RECEIVED>>

The process is the same either way, just a matter of whether you want to have to include a WebBrowser control in your form. PINs are only good for a short time, so you must use it to get an access token right away.

C. Get Access token

' imgUrResults is an enum exposed by the class
Dim result As imgurAPI.imgUrResults = imgUR.RequestToken

Notes:

• the imgUR class will retain the token
• tokens currently expire in 1 hour (3600 seconds)

D: Upload a File
Upload using imgUR.UploadImage(filename, boolAnon)

Filename - the file to upload

boolAnon - Boolean flag. False = upload this file to your account vs the Anon general pool method.

Example:

' get token
Dim result As imgurAPI.imgUrResults = imgUR.RequestToken

' check result
If result = imgurAPI.imgUrResults.OK Then
    ' assumes the file exists
    imgUR.UploadImage("C:\Temp\London.jpg", False)
Else
    MessageBox.Show(String.Format("Error getting access token. Status:{0}",
        result.ToString))
End If

After the file uploads, the procedure looks for the link in the response. If the link can be parsed, it will be available from the LastImageLink property and pasted to the ClipBoard as well.

Misc Properties, Settings and Methods

LastImageLink (String) - URL of the last image uploaded

UseClipBoard (Bool) - When true, imgurAPI class posts the link to the uploaded image to the Clipboard

TokenExpiry (Date) - The DateTime that the current token expires

GetTokenTimeRemaining() As TimeSpan - A TimeSpan representing how long before the current token expires

Public Function GetTokenCountdown() As String - Formatted string of TimeRemaining

Public WriteOnly Property Pin As String - the PIN required to get an access token

Public Function IsTokenValid() As Boolean - is the current token valid

Public Function IsTokenExpired() As Boolean - simple Boolean version of TimeRemaining vs DateTime.Now

Notes

• Tokens can be renewed or extended. But since they last for an hour, this seems plenty.
• PINS are only good for a short time. Once a PIN is exchanged for a token the imgurAPI (this class) clears the PIN. If there is a problem getting the Token, you will have to get a new PIN first (or paste the last one if you just got it a few minutes ago).
• Uploaded images are not visible to the world at large unless/until you change the setting on your account.
• You can reset your SecretID (Settings -> Applications). If you do, you will need to also reset it for apps using this API class, and recompile (or read it from a config file).

If you use a WebBrowser control to get a PIN, you can add this code to the DocumentCompleted event to scrape the PIN from the HTML:

' wb is the control
Dim htmlDoc As System.Windows.Forms.HtmlDocument = wb.Document
Dim elP As System.Windows.Forms.HtmlElement = htmlDoc.GetElementById("pin")

If elP IsNot Nothing Then
    sPin = elP.GetAttribute("value")
    If String.IsNullOrEmpty(sPin) = False Then
       ' user has to push the button for `imgUR.Pin = tbPIN.Text`
       ' this is in case the HTML changes, the user can override
       ' and input the correct PIN
       Me.tbPIN.Text = sPin
    End If

End If

---

About the OAuth Model

this is unofficial - info learned from reading the docs and working with the API. Applies to imgur API v3 as of this date.

There is nothing automated about getting a PIN. One way or another you must navigate to a URL in a browser and enter your account name and Password to get a PIN. This is by design so that you, yourself, personally are authorizing some external app to access your account content.

Method One above uses a .NET WebBrowser control to do this. With this method we can be sure that both you and the imgur class are using the same Endpoint/URL because it sends you there via the browser control.

Method Two is just you go there in some browser, any browser. Log in, get a PIN, and paste it to the imgurAPI class.

No matter the method, the correct Endpoint/URL to use is:

https://api.imgur.com/oauth2/authorize?client_id=YOUR_CLIENT_ID&response_type=pin&state=foobar

Using a browser on the form using the imgurAPI class, we obviously we can be sure that both you and the class are using the same URL and ClientID. The code for DocumentComplete fetches the PIN into the TextBox only you still need to set it in the class:

myimgUR.PIN = tbPinCode.Text

PINS are single use, and expire.

So when developing especially, and you stop the code, add some stuff then rerun naturally, the code will no longer have the old Token or PIN. If the last PIN was recent and not submitted, you might not have to get a new one, but I find it is hard to remember if that is the case.

The class treats PINS as single use. Once a Token has been received, it clears out the variable since they have been used and are no longer valid.

---

Final Edit

• Added an Anon Only mode

To use the class to upload ONLY in Anon mode (to the general site, not your account), the SecretID is not needed. For this, use the new constructor overload:

Public Sub New(clientID As String)

This sets the class to work an Anon ONLY and certain methods will return an error or throe an exception when using Account based methods such as GetToken. If you initialize it with just ClientID, it remains in AnonOnly mode until you recreate the object with the both the ClientID and SecretID.

There is no real reason to use it as AnonOnly (unless you do not have an account) since the UploadImage method allows you to specify it as an Anon upload by file:

Function UploadImage(filename As String, 
                     Optional Anon As Boolean = False) As imgUrResults

• Revised/clarified the imgUrResults Enum

This is meant to be all-encompassing: some returns indicate a problem detected by the class, others are server responses which are simply passed along.

• Removed IsTokenExpired

IsTokenValid is more thorough. There are other methods to get the time remaining or the actual Expiry.

• Added assorted error trapping/handling
  • Check for a valid WebBrowser control when requesting a PIN
  • Refined the method used to get the server status code after an image is uploaded
  • Reworked some handling to give prioritize remote server status over class returns

.